slachiewicz opened a new issue, #50957:
URL: https://github.com/apache/arrow/issues/50957
### Describe the bug, including details regarding any error messages,
version, and platform.
`pa.concat_tables` accepts `**kwargs` but only ever inspects `promote`.
Every other keyword is dropped without a warning or an error:
```python
>>> import pyarrow as pa
>>> t1 = pa.Table.from_pydict({'a': [1.0]})
>>> t2 = pa.Table.from_pydict({'a': [2.0]})
>>> pa.concat_tables([t1, t2], totally_bogus_kwarg=123).num_rows
2
```
https://github.com/apache/arrow/blob/main/python/pyarrow/table.pxi#L6318-L6339
Two ways this bites:
1. A typo in a keyword is silently ignored rather than raising `TypeError`,
which is what a reader would expect from a normal Python signature.
2. `unify_schemas` in particular looks like it should work. It is a real
field on the underlying `ConcatenateTablesOptions`, R's `concat_tables()` takes
a `unify_schemas` argument, and the C++ option is what `promote_options` sets
on the caller's behalf. So this reads as if it silently does the opposite of
what was asked:
```python
>>> pa.concat_tables(
... [pa.Table.from_pydict({'a': [1]}), pa.Table.from_pydict({'a':
[1.0]})],
... unify_schemas=False,
promote_options="permissive").schema.field('a').type
DataType(double)
```
Schemas were unified despite `unify_schemas=False`.
This surfaced in GH-38809, where the reporter passed `unify_schemas=True`
and reasonably assumed it had an effect. The type-promotion half of that issue
is fixed; this half is not.
A fix could be either to raise `TypeError` on unrecognised keywords, keeping
`**kwargs` only for the deprecated `promote`, or to retire `promote` altogether
(it has warned `FutureWarning` since 14.0.0) and give `concat_tables` an
explicit signature with no `**kwargs`. The second is a breaking change and
would need its own deprecation window; the first is not.
Reproduced on pyarrow 25.0.1, macOS/arm64, and the code path is unchanged on
`main`.
### Component(s)
Python
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